v10.15.0 NLI decision layer: entailment-based dedup confirm, contradiction detection, Nyx phase-4 finder

Replaces the cross-encoder reranker for the store DECISION questions (is this a duplicate? does this contradict?) with natural-language-inference models. A reranker scores topicality ("same topic?"); NLI scores polarity ("same claim? opposite claim?"), which is the question the store layer actually asks. Backed by a 114-pair benchmark on real production memories (benchmarks/nli-bench): contradiction AUC 0.939 vs 0.69 for the reranker (which produced ~40 false positives of 96 negatives at its best threshold); dedup AUC 0.983 with 1 false positive vs 16-21 false blocks for the raw vec-distance blocker. The reranker keeps its search-ranking role, where topicality is the right signal.

Added

• mnemos/nli.py: NLI scoring layer. Language-agnostic routing: content that reads as English (cheap stopword heuristic, is_english()) uses an English ANLI+FEVER-hardened checkpoint (strongest benched); everything else uses a multilingual XNLI checkpoint (~100 languages). p_contradiction() takes the max over both premise/hypothesis directions (real contradictions score asymmetrically: 0.44 one way, 0.99 the other on the bench); bidirectional_entailment() takes the min (a duplicate entails in both directions); line_max_contradiction() scores the top-k cosine-preselected line pairs of two records, rescuing conflicts that blob-level scoring buries (benched: a diagnosis conflict scored 0.58 blob-level, 0.9956 line-level).
• MNEMOS_DEDUP_CONFIRM=nli: store-path dedup confirm tier. Bidirectional entailment >= MNEMOS_NLI_DEDUP_THRESHOLD (default 0.85) on the top MNEMOS_NLI_DEDUP_MAX_CANDIDATES (default 3) candidates by vector distance blocks the store; below it the store proceeds with no fall-through to the coarser scorers. Legacy behavior unchanged when unset or when the NLI runtime is unavailable.
• MNEMOS_CONTRADICT_MODE=nli: contradiction detection asks the NLI question directly after the vec gate. Warn + contradicts link only at max-direction P(contra) >= MNEMOS_NLI_CONTRA_THRESHOLD (default 0.98). No relates band: WEAVE owns topical linking.
• MNEMOS_NYX_CONTRADICT_FINDER=nli: phase-4 candidate finder. Drops the legacy cosine-band CEILING (near-identical pairs are where real contradictions live) and scores floor-gated pairs with the line-level finder, recall-first (MNEMOS_NLI_FINDER_THRESHOLD, default 0.8, capped at MNEMOS_NLI_FINDER_MAX_PAIRS pairs); the existing LLM judge keeps precision. The three benched real contradictions the blob/band approach missed are all caught by this path.
• Optional dependency extra mnemos[nli] (torch, transformers, sentencepiece). Every NLI entry point degrades gracefully when the extra is not installed.
• tests/test_v1015_nli.py: 19 tests (routing, direction aggregation, store integrations, phase-4 selection), model-free via stub scorers.

Changed

• Phase-4 cosine gates CONTRADICT_MIN_SIM/CONTRADICT_MAX_SIM moved from consolidation/phases.py to constants.py (env-overridable); all new NLI tunables live in constants.py as the single settings surface.
• Phase-4 pair selection extracted into select_contradict_candidates() (pure, testable).
• scripts/mnemos_sortkit.py no longer defaults to a deployment-specific namespace.